PXE document for UEFI environment
They are some devices that doesn't have the Compatibility Support Module nor supporting legacy boot. The syslinux files for those UEFI only devices are different
It would be
syslinux.efi
ldlinux.e64
libutil.c32
libcom32.c32
menu.c32
Also I would suggest using http instead tftp for initramfs image likes, which it would be more fast and stable than tftp, the syslinux for UEFI would support http protocols as it is new enough
INITRD sysresccd/boot/intel_ucode.img,sysresccd/boot/amd_ucode.img,http://192.168.10.3/sysresccd.img